[R] how ot replace the diagonal of a matrix

[jim holtman]

try:

> mps <- matrix(rep(.4, 3*3), nrow=3, byrow=TRUE)
> idx <- diag(3)
> mps
     [,1] [,2] [,3]
[1,]  0.4  0.4  0.4
[2,]  0.4  0.4  0.4
[3,]  0.4  0.4  0.4
> idx
     [,1] [,2] [,3]
[1,]    1    0    0
[2,]    0    1    0
[3,]    0    0    1
> mps[idx == 1] <- rep(.6,3)
>
> mps
     [,1] [,2] [,3]
[1,]  0.6  0.4  0.4
[2,]  0.4  0.6  0.4
[3,]  0.4  0.4  0.6
>


On 10/3/06, roger bos <roger.bos at gmail.com> wrote:
> Dear useRs,
>
> Trying to replace the diagonal of a matrix is not working for me.  I
> want a matrix with .6 on the diag and .4 elsewhere.  The following
> code looks like it should work--when I lookk at mps and idx they look
> how I want them too--but it only replaces the first element, not each
> element on the diagonal.
>
> mps <- matrix(rep(.4, 3*3), nrow=n, byrow=TRUE)
> idx <- diag(3)
> mps
> idx
> mps[idx] <- rep(.6,3)
>
> I also tried something along the lines of diag(mps=.6, ...) but it
> didn't know what mps was.
>
> Thanks,
>
> Roger
>
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-- 
Jim Holtman
Cincinnati, OH
+1 513 646 9390

What is the problem you are trying to solve?